Permanent magnets are used for several important applications, including DC electrical motors, wind turbines, hybrid automobile, and for many other applications. Modern widely used rare-earth based permanent magnet materials, such as Sm—Co and Nd—Fe—B, are generally intermetallic alloys made from rare earth elements and transition metals such as cobalt. They derive their exceptional magnetic properties from the combination of the rare earth elements sub-lattice providing the high magnetic anisotropy and the 3-D sub-lattices of Fe or Co giving a large magnetization and a high Curie temperature. However, the high costs of rare earth elements make the widespread use of these permanent magnets commercially unattractive.
Thus, finding a viable alternative to rare-earth based permanent magnets has become critical to decrease their cost and make them commercially viable for various applications. The present work focuses on producing permanent magnetic material, with good magnetic properties, which is free from rare-earth elements and thus cost-effective.
There are many known permanent magnetic material in the literature synthesized by different research groups.
Reference is made to Zeng et.al. (Journal of Applied Physics 99, (2006) pp. 08E90201-03) wherein the synthesis of τ-MnAl was carried out by arc melting under an argon atmosphere subsequently heating to 1150° C. and holding for 20 h followed by water quenching. Then the quenched material was crushed and milled in argon for 8 h in a hardened steel vial using a SPEX 8000 mill using hardened steels balls with a ball-to-charge weight ratio of 10:1. Samples were annealed at temperatures from 350 to 600° C. for 10 min to produce the ferromagnetic τ-MnAl. The resulting material exhibited magnetic properties, coercive field of 4.8 kOe and saturation magnetization 87 emu/g for powder annealed at 400° C. for 10 min.
Yet another reference is made to Liu et.al. (J Mater Sci vol. 47 (2012) pp. 2333-2338), wherein MnAl alloys with C doping was prepared by argon arc melting. The melted samples were used to prepare ribbon samples by a single-roller melt spinning technique under protective atmosphere (argon) at a wheel speed of 40 m/s. The as spun ribbons were annealed at 500-650° C. for 10 min. in Argon. The effects of composition and heat treatment on the phase transition and hard magnetic properties were investigated. Addition of C was found beneficial to the formation of the τ MnAl. Addition carbon modifies TC of τ phase. 2% C addition reduced the TC from 346 to 258° C. The Mn53.3Al45C1.7 ribbon after annealing at 650° C. for 10 min exhibited best combined magnetic properties i.e. saturation polarization 0.83 T, remanence 0.30 T, coercivity 123 kA/m, and maximum energy product 12.24 kJ/m3.
Yet another reference is made to Rao et.al. (J. Phys. D: Appl. Phys. Vol. 46 (2013) pp. 062001-04), wherein MnBi ingot was prepared by argon arc-melting. The ingot was annealed at 573K for 24 h in vacuum to obtain the LTP MnBi. The annealed alloy ingots were manually crushed and Low Energy Ball Milled for different milling times up to 8 h in a hardened stainless steel vial using rotary mill with rotation speed of 150 rpm. The milling was performed in hexane with hardened-steel balls 4-12 mm in diameter. The ball-to-powder weight ratio was about 15:1. The milled powders were compacted at room temperature in the presence of a 1.8 T magnetic field. The green compacts were then placed into a tungsten carbide die and subjected to hot compaction at 593K for 10 min with an applied pressure of 300 MPa under vacuum (better than 4×10−5 mbar.). Maximum energy product of 5.8 MGOe at room temperature and 3.6 MGOe at 530K has been obtained in synthesized MnBi.
Yet another reference is made to Journal of Applied Physics vol. 112, (2012) pp. 083901-04, wherein Mn100-xGax (x=20-50) alloy ingots were prepared by argon arc melting. The melted samples were used to prepare ribbon. As spun ribbons were heat treated in an argon atmosphere at temperatures between 573K and 1073K for 1 h. A maximum coercivity value of 5.7 kOe was achieved in the Mn70Ga30 melt-spun ribbon annealed at 973K for 1 h.
The present invention describes the synthesis of a new permanent magnet material, boron doped manganese antimonide which is free from rare-earth elements with good magnetic properties.